Patent US4439271A successfully refreshed from Google Patents.
US4439271A
Expired / Lapsed
US
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Process for the oxygen bleaching of cellulose pulp
Assignee: Mo och Domsjo AB
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Filing: 1981-06-04
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Granted: 1984-03-27
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Expires: 2001-06-04
Abstract
Abstract A two-stage oxygen bleaching of chemical cellulose pulp is provided, in which an alkaline oxygen bleaching stage is preceded by a nitrogen dioxide activating stage in which oxygen is added to the activating stage in an amount such that nitrogen monoxide formed as an intermediate during the activation process is consumed, so regulating the amount of oxygen added that when the activation reaction is practically complete, substantially all of the nitrogen dioxide and nitrogen monoxide has been consumed.
Inventors
- 👤 Hans O. Samuelson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 08:35
CPC Classifications
D; D21; D21C; D21C9/00; D21C9/10; D21C9/1005
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
236 words
A two stage process for the delignification of cellulose pulp, including chemical pulp prepared from the digestion of lignoscellulosic material, including an activation stage followed by an oxygen gas bleaching stage, the activation stage leading to a quick delignification in the oxygen gas bleaching stage, and also to a deactivation of the pulp in such a manner that degradation of the carbohydrates during the oxygen gas bleaching stage becomes slower, which comprises bringing the cellulose pulp in the activation stage in the presence of water in contact with a gas phase containing nitrogen dioxide and modifying the lignin content of the cellulose pulp to increase the rate of delignification in the oxygen gas bleaching stage by reaction with nitrogen dioxide over a reaction time within the range from about 5 seconds to about 30 minutes; adding oxygen gas to the activating reaction in an amount within the range from about 0.1 to about 5 moles per mole of NO 2 and in an amount within the range from about 0.6 to about 5 moles per mole of NO, nitrogen monoxide formed in the activation being utilized in the activation reaction; and then in the oxygen gas bleaching stage, subjecting the pulp to an oxygen gas bleaching in the presence of an alkaline-reacting neutralization medium or neutralizing agent, thereby obtaining an increased rate of delignification and a reduced degradation of the carbohydrates during the oxygen gas bleaching.
Claim 2
Dependent Claim
236 words
A two stage process for the delignification of cellulose pulp, including chemical pulp prepared from the digestion of lignoscellulosic material, including an activation stage followed by an oxygen gas bleaching stage, the activation stage leading to a quick delignification in the oxygen gas bleaching stage, and also to a deactivation of the pulp in such a manner that degradation of the carbohydrates during the oxygen gas bleaching stage becomes slower, which comprises bringing the cellulose pulp in the activation stage in the presence of water in contact with a gas phase containing nitrogen dioxide and modifying the lignin content of the cellulose pulp to increase the rate of delignification in the oxygen gas bleaching stage by reaction with nitrogen dioxide over a reaction time within the range from about 5 seconds to about 30 minutes; adding oxygen gas to the activating reaction in an amount within the range from about 0.1 to about 5 moles per mole of NO 2 and in an amount within the range from about 0.6 to about 5 moles per mole of NO, nitrogen monoxide formed in the activation being utilized in the activation reaction; and then in the oxygen gas bleaching stage, subjecting the pulp to an oxygen gas bleaching in the presence of an alkaline-reacting neutralization medium or neutralizing agent, thereby obtaining an increased rate of delignification and a reduced degradation of the carbohydrates during the oxygen gas bleaching.
Claim 3
Dependent Claim
36 words
A process according to claim 1 in which the total amount of nitrogen dioxide during activation is within the range from about 3 to about 300 gram moles calculated per 100 kg of dry cellulose pulp.
Claim 4
Dependent Claim
19 words
A process according to claim 1 in which the total pressure during the activation is maintained below atmospheric pressure.
Claim 5
Dependent Claim
22 words
A process according to claim 1 in which the partial pressure of nitrogen oxide during the activation is maintained beneath 0.5 bar.
Claim 6
Dependent Claim
46 words
A process according to claim 1 in which at least one compound selected from the group consisting of oxygen, nitrogen dioxide and nitrogen monoxide is added continuously in the course of the activation reaction to provide a uniform distribution throughout the whole of the cellulose pulp.
Claim 7
Dependent Claim
21 words
A process according to claim 1 in which the cellulose pulp is chemical cellulose pulp prepared using an alkaline pulping liquor.
Claim 8
Dependent Claim
25 words
A process according to claim 6 in which the chemical pulp is selected from the group consisting of sulfate pulp, polysulfide pulp and soda pulp.
Claim 9
Dependent Claim
14 words
A process according to claim 1 in which the cellulose pulp is sulfite pulp.
Claim 10
Dependent Claim
34 words
A process according to claim 1 in which after the activation stage, the pulp is washed with water or an aqueous solution before addition of alkaline neutralization medium in the oxygen gas bleaching stage.
Claim 11
Dependent Claim
16 words
A process according to claim 9 in which the aqueous solution is oxygen gas bleaching liquor.
Claim 12
Dependent Claim
31 words
A process according to claim 9 in which the cellulose pulp after the activation stage is washed with water or an aqueous solution under such conditions that an acid solution results.
Claim 13
Dependent Claim
25 words
A process according to claim 11 in which the washed pulp is treated with an alkaline-reacting solution at from about 20° to about 100° C.
Claim 14
Dependent Claim
31 words
A process according to claim 12 in which the solution is waste liquor from oxygen gas bleaching, and a part of the modified lignin is extracted out of the activated pulp.
Claim 15
Dependent Claim
23 words
A process according to claim 1 in which before the oxygen gas bleaching stage, the pulp is impregnated with an alkaline-reacting neutralization medium.
Claim 16
Dependent Claim
33 words
A process according to claim 14 in which at least one additive selected from the group consisting of magnesium compounds, complexing agents, formaldehyde, and phenylene diamine is present during the oxygen gas bleaching.
Claim 17
Dependent Claim
23 words
A process according to claim 15 in which the complexing agent is selected from the group consisting of aminopolyphosphonic acids and aminopolycarboxylic acids.
Claim 18
Dependent Claim
29 words
A process according to claim 15 in which a complexing agent is added and then any complexed transition metal compounds removed prior to the oxygen gas bleaching delignification stage.
Claim 19
Dependent Claim
27 words
A process according to claim 17 in which another complexing agent is added so that a complexing agent is present during the oxygen gas bleaching delignification stage.
Claim 20
Dependent Claim
28 words
A process according to claim 15 in which a complexing agent is added, in an amount within the range from about 0.2 to about 1 kg/ton of pulp.
Claim 21
Dependent Claim
38 words
A process according to claim 19 in which the complexing agent is supplied to the pulp in solution at a pH below 7.5, and the complex-forming reactions allowed to proceed for a time of up to ninety minutes.
Claim 22
Dependent Claim
45 words
A process according to claim 19 in which at least one complexing agent is added that provides manganese complexes which at a pH 9 have a stability constant which is at least 1000 times greater than the corresponding stability constant for any magnesium complexes present.
Claim 23
Dependent Claim
26 words
A process according to claim 15 in which formaldehyde is added in an amount of at least 0.5%, based on the dry weight of the pulp.
Claim 24
Dependent Claim
15 words
A process according to claim 1 in which the process is repeated at least once.
Claim 25
Dependent Claim
21 words
A process according to claim 1 in which the pulp consistency is within the range from about 2 to about 40%.
Claim 26
Dependent Claim
28 words
A process according to claim 1 in which the total alkali addition during the oxygen gas bleaching delignification is within the range from about 1 to about 10%.
Claim 27
Dependent Claim
42 words
A process according to claim 1 in which the treatment time for the oxygen gas bleaching delignification stage is within the range from about 60 to about 500 minutes at a temperature within the range from about 90° to about 135° C.
Claim 28
Dependent Claim
25 words
A process according to claim 1 in which the temperature during the activation is maintained within the range from about 0° to about 100° C.
Claim 29
Dependent Claim
31 words
A process according to claim 27 in which temperature during the activation is maintained within the range from 80° to 100° C. and the reaction time does not exceed 250 seconds.
Claim 30
Dependent Claim
30 words
A process according to claim 27 in which temperature during the activation is maintained below 80° C. and the reaction times is within the range from 5 to 30 minutes.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-03-27 | 1987-09-26 | 1988-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-03-27 | 1991-09-26 | 1992-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-03-27 | 1995-09-26 | 1996-03-27 | $7700.00 | Window Closed / Lapsed |